1. Field of the Invention
The present invention relates to the field of transmitter technology. In particular it concerns an antenna selector in the form of a switching matrix for the optional connection of a plurality of transmitters to a plurality of antennae, in which antenna selector
on a first level a plurality of first feeder lines are arranged parallel to one another, one transmitter connection being associated with each of the first feeder lines; PA1 on a second level parallel to the first level a plurality of second feeder lines are arranged parallel to one another and at right angles to the first feeder lines, one first antenna connection being associated with each of the second feeder lines; PA1 there is provided at the intersections of the first and second feeder lines in each case a switch which has a corresponding switching level on each of the levels, and which in a first switching position connects through individually the associated first feeder line and the associated second feeder line, and in a second switching position disconnects the associated first and second feeder line and mutually connects them. An antenna selector of this kind is known, for example, from the Swiss Patent Specification 298,004. PA1 there are arranged on a third level parallel to the first two levels a plurality of third feeder lines parallel to one another and at right angles to the first feeder lines, a second antenna connection being associated with each of the third feeder lines; PA1 the intersections of the first and third feeder lines coincide with corresponding intersections of the first and second feeder lines; and PA1 each switch has a switching level corresponding to the third level, and in the first switching position also connects through the associated third feeder line, in the second switching position also disconnects the associated third feeder line, and in a third switching position disconnects all three associated feeder lines and only mutually connects the associated first and third feeder line.
2. Discussion of Background
Large transmitter systems, in particular shortwave transmitting stations, contain, except in special cases, a large number of antennae since the most favourable operating frequencies change, for example, depending on the time of day or year, and moreover depend on the transmission distance and the geographic direction, but the antennae usually cover in each case only a narrow frequency range. Since, moreover, directional radiation is for the most part employed, several antennae are usually required for each direction.
Owing to the versatility of the transmitting program, such transmitting systems usually also contain a plurality of transmitters.
Full utilization of the transmitting system is therefore only provided if there is a clear and quick switchover device which is simple to operate and reliable and which permits each of the transmitters to be connected to each of the antennae as desired.
Since the transmitting systems as a rule contain a greatly differing number of transmitters and antennae, and since existing systems are also frequently expanded later, it is particularly expedient and economic to build the switchover device in modular fashion. Such an antenna selector in the form of a matrix has been described in the publication mentioned at the beginning.
The rows of the matrix are associated there with the transmitters, and the columns of the matrix with the antennae. The elements of the matrix are formed by individual switches.
In the known antenna selector, the switching operation takes place on two levels: on the first level there run first feeder lines parallel to one another which are fed by the transmitters and which correspond to the rows of the matrix.
On the second level there run, likewise parallel to one another, but at right angles to the first feeder lines, second feeder lines which feed the radio-frequency power of the transmitter into the antennae and which correspond to the columns of the matrix.
Since the two levels are arranged above one another, the first and second feeder lines intersect. At these intersections there are then in each case switches with two switching levels. Each switching level corresponds to a feeder line level.
In the conventional matrix, the switches have two switching positions: in the first switching position the first feeder line running through the respective intersection is connected through on the one switching level. The same takes place on the other switching level with the corresponding second feeder line. Both feeder lines conduct the radio-frequency power through this intersection without interference and without changing the direction.
In the second switching position, both through connections are cancelled. Instead, the switch end of the first feeder line is connected up to the switch beginning of the second feeder line via a fixed wire bridge which runs within the switch between the two switching levels. A diagonal line connection results which redirects the power fed in by the transmitter to the antenna associated with the switch. Depending on the switching position of the switch, each transmitter can thus be connected to each antenna (even in different ways).
In the case of large shortwave transmitting systems in which each transmitter has in a frequency range of approximately 3-30 MHz outputs of several 100 kW, and the feeder lines are designed as symmetrical lines with a wave impedance of, for example, 300 ohm, each of the cuboid switches has a depth of approximately one meter and a base area of approximately 0.5.times.0.5 m.sup.2.
If such a transmitting system now contains T.sub.n transmitters and A.sub.m antennae, for the known antenna selector EQU S.sub.K =T.sub.n .multidot.A.sub.m
switches are required, which are all combined beside one another to form a matrix. With only four transmitters (T.sub.n =4) and sixteen antennae (A.sub.m =16), this already amounts to S.sub.K =64 individual switches, which not only require a considerable space, but which must all be equipped individually with corresponding motor drives and monitoring and control elements. This entails a considerable outlay, which forms a decisive part of the costs for the overall transmitting system.